OT : Critical speed of a hollow shaft

I don't have a spreadsheet, but I do think there are a couple addtional wrinkles for the analysis beyond the simple shaft material, bearing supports and size and a uniform load. Stiffness or looseness of the load would change the analysis.

The natural frequency of the loaded assembly could allow vibrations to form which greatly raise the stress on the hollow shaft beyond what a simple calculation might suggest is safe.

The only time I worked on something like this was in high speed sawmill equipment, before I finished college. When running a shaft with sawblades and spacers @ 3600 rpm on a shaft, if there was an out of balance condition, it could set up self-destructive vibrations, and bearings were the first to fail in that case.

Bo

"Bo" wrote in >

Bo,

I agree that it's likely to be more complex. In this particular app, there is a rubber coated roll pressed against a hard roll, and this can cause bowing of the rolls and hence eccentricities. I'm really looking to ensure I'm a long way away from the theoretical critical speed of a simplified system - say, at only 20-30% of it max.

John H

there are a couple

Can you inquire from suppliers of printing rolls or look at their catalogs and determine with reasonable accuracy the printing roll geometry? I think I've seen suppliers of printing rolls and their coatings advertised by companies that repair and rebuild printing rolls.

Bo